Spark plug with resilient connector to electrical resistor



R. c. ZELLER 3,205,402

SPARK PLUG WITH RESILIENT CONNECTOR 'I'O ELECTRICAL RESISTOR Sept. 7,1965 Filed Sept. 10, 1962 wmw FIG.7.

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ROBERT C. ZELLER ATTORNEYS United States Patent 3,205,402 SPARK PLUGWITH RESILIENT CONNECTOR TO ELECTRICAL RESISTOR Robert C. Zeller,Defiance, Ohio, assignor to The Zeller Corporation, Defiance, Ohio, acorporation of Ohio Filed Sept. 10, 1962, Ser. No. 222,393 14 Claims.(Cl. 315-59) The invention relates to spark plugs. More particularly theinvention relates to an improved construction of shielded resistor-typeelectrode insulator assembly.

In the present state of the art of shielded spark plugs, it is usual toprovide a metal plug which can be pressed into engagement with internalthreads in the insulator. This plug forms an abutment for one end of aspring which exerts pressure on the resistor to maintain it in contactwith the electrode.

My invention provides an improved closure construction to be used inplace of the conventional plug. The advantages of my construction overthe prior art will be more clearly apparent from the detaileddescriptionand the accompanying drawings wherein:

FIGURE 1 is a longitudinal section through a spark plug.

FIGURE 2 is a longitudinal section through the insulator showing amodified form of closure.

FIGURES 3 to 8 inclusive are views similar to FIG- URE 2 showing othermodifications of the invention.

FIGURE 9 is a side elevation of the spring closure prior to assembly.

FIGURE 10 is a top plan view thereof.

My invention in its broadest aspects contemplates a closure constructionconsisting essentially of a single part so constructed and arranged asto exert resilient pressure against the electrical resistor and also toengage the insulator in such a manner that it cannot be removedaccidently or by any normal means. The single part constituting theclosure is in the form of a coil spring constructed from spring wire andhaving a novel configuration to provide for the several functions whichit is designed to accomplish.

As illustrated in the drawings, 10 is a standard spark plug ceramicinsulator having the enlarged outer portion 10a for engagement with themetallic shell 11 of the spark plug. Above the enlargement the ceramicinsulator is generally cylindrical as shown at 13 and below theenlargement is the tapering nose portion 14. The insulator has a centralbore 15 extending through its entire length. The bore is enlarged at 16in the upper portion forming a shoulder 17. Below this shoulder the boreis provided with internal threads 18 which are preferably of the woodscrew type. Within the nose portion of the insulator is the centerelectrode 19, the outer end of which projects slightly beyond the noseof the insulator to form a spark gap with the ground electrode 20. Thecenter electrode is secured to the ceramic in the conventional manner.Between the inner end of the center electrode 19 and the threadedportion of the insulator is a standard cartridge type electricalresistor 21. The resistor may be inserted into the bore after theelectrode is secured in position.

The present invention relates to an improved form of closure forretaining the electrical resistor 21 under pressure in contact withelectrode 19. As shown in FIGURE 1, the closure 22 is constructed from asingle piece of spring wire 23. The intermediate convolutions 24 have anormal diameter which is slightly larger than the bore 18 and there areseveral convolutions of this size. At one end there are a series ofconvolutions or loops 25 of smaller diameter than the bore 15terminating at the inner end 26. At the opposite end the wire is formedinto a spiral 27 lying in a plane transverse to the longitudinal axis ofthe insulator. The spiral 27 has outer- 3,205,402 Patented Sept. 7, 1965most convolutions 28 of larger diameter than the bore 15, which form ineffect an enlarged integral head adapted to seat on the ceramic shoulder17. In assembly, the closure 24 is inserted through the enlarged bore 15with the small end toward the resistor 21. Axial pressure is applied tothe spiral convolutions 27, 28 thereby causing the intermediateconvolutions 24 to contract in diameter sufiicient to move through thebore 15 until the inner end 26 is in pressure contact with the resistor.The axial pressure is continued until the spring head is seated on theceramic shoulder whereupon the spring tension in the contractedconvolutions causes them to expand and to engage the internal threads ofthe ceramic thereby securely interlocking the closure to the ceramicinsulator.

In the modified construction of FIGURE 2, the closure is the same as inFIGURE 1 except that the head is formed by convolutions arranged indome-shape 29.

In FIGURE 3 the head of the closure is formed by the outer convolutions30, as in FIGURE 1, but the spiral convolutions in the transverse planeterminate without extending inwardly beyond the diameter of theconvolutions 24. Instead of these inwardly continuing convolutions aseperate metallic cap 31 is provided having the inturned lip 32 forengaging beneath the outer loop 30.

In FIGURE 4 a modified cap 33 has an outer flange 34 for engaging theceramic shoulder thereby completely eliminating the spiral spring headof FIGURE 1. The cap 33 has a shank 35 with a peripheral groove 36 forengaging the end convolution of the intermediate group 24. In FIGURE 5 adisc 37 is provided of such diameter relative to the upper spring loopthat, in assembly by axial pressure, the disc 37 will temporarily pushthe top loop 38 over the second loop 39. When the disc reaches thesecond loop 39, the top loop 38 will snap back over the disc and theparts will assume the positions illustrated in FIGURE 5.

FIGURES 6 and 7 are modifications of the device shown in FIGURE 1. Thesmall diameter loops 25 are eliminated so that the resistor 21 canextend within the intermediate convolutions 24 as illustrated. Pressureon 1 the resistor is provided by means of a depending coil spring 40.This can be formed by continuing the inner end of the spring wireforming the spiral 27 and shaping this inner end into the small diametercoil 40.

In FIGURE 8 the bore of the ceramic insulator is not internally threadedbut instead is provided with a single annular groove 41. The coil springclearance is of the same type as illustrated in FIGURE 1 and afterinserting this closure into the bore by axial pressure, the springexpands into the annular groove and locks itself in position whilecontinuing to exert axial pressure on the electrical resistor 21.

FIGURES 9 and 10 illustrate the spring closure prior to insertion in theinsulator. The spring shown in FIG- URE 8 is substantially the same asthe one shown assembled in FIGURE 1 except that the spring of FIGURE 9has one additional loop 40. This loop is of the same diameter as theoutermost loop 28 but is arranged immediately below the plane of thespiral 27.

What I claim as my invention is:

1. A spark plug comprising a ceramic insulator having a central borewith an internally threaded portion, an electrode within the bore ofsaid ceramic insulator and extending outwardly from one end thereof, anelectrical resistor between said electrode and said internally threadedportion, and a coil spring bearing on said resistor and havingconvolutions directly engaging said internally threaded portion.

2. A spark plug comprising a ceramic insulator having a central bore, anenlarged counterbore forming a shoulder therebetween, said central borebeing internally threaded adjacent said shoulder, an electrode withinsaid central bore extending outwardly from one end thereof, anelectrical resistor between said electrode and said internally threadedportion, and a coil spring bearing on said resistor and havingconvolutions directly engaging said internally threaded portion.

3. A spark plug comprising a ceramic insulator having a central bore, anenlarged counterbore forming a shoulder therebetween, said central borebeing internally threaded adjacent said shoulder, an electrode withinsaid central bore extending outwardly from one end thereof, anelectrical resistor between said electrode and said internally threadedportion, a coil spring having intermediate convolutions directlyengaging said internally threaded portion and having a portion at oneend thereof which is of enlarged diameter and extends within saidcounterbore to seat upon said shoulder.

4. A spark plug as in claim 3 in which said portion of enlarged diameterhas spiral convolutions in a plane transverse to said counterbore.

5. A spark plug in accordance with claim 3 in which said enlargedportion of the spring has convolutions arranged to form a dome shapedhead.

6. A spark plug comprising a ceramic insulator having a central bore, anenlarged counterbore forming a shoulder therebetween, said central borebeing internally threaded adjacent said shoulder, an electrode withinsaid central bore extending outwardly from one end thereof, anelectrical resistor between said electrode and said internally threadedportion, a coil spring having intermediate convolutions directlyengaging said internally threaded portion and having a portion at oneend thereof which is of enlarged diameter and extends within saidcounterbore and having a metal cap within said counterbore With aninturned lip engaging beneath a spring convolution within saidcounterbore and seating upon said shoulder.

7. A spark plug in accordance with claim 3 in which said coil spring hasan additional coil of smaller diameter in contact with said electricalresistor.

8. A spark plug in accordance with claim 3 in which said coil spring hasconvolutions of smaller diameter between said intermediate convolutionsand said electrical resistor.

9. A spark plug in accordance with claim 3 in which said coil spring hasconvolutions of smaller diameter between said portion of enlargeddiameter and said electrical resistor.

10. A shielded spark plug comprising a ceramic insulator having acentral bore with an internal groove therein, an electrode within thebore of said ceramic insulator extending outwardly from one end thereof,an electrical resistor within said bore between said electrode and saidinternal groove, and a coil spring bearing on said resistor and havingconvolutions directly engaging said internal groove.

11. A shielded spark plug in accordance with claim 10 in which saidinternal groove is an annular groove in a plane transverse to saidelectrode.

12. A spark plug comprising a ceramic insulator having a central bore,an enlarged counterbore forming a shoulder therebetween, said centralbore having an internal groove therein adjacent said shoulder, anelectrode within said central bore extending outwardly from one endthereof, an electrical resistor between said electrode and saidshoulder, a coil spring bearing on said resistor and having convolutionsdirectly engaging said internal groove, said coil spring having aportion at one end thereof which is of an enlarged diameter and extendswithin said counterbore.

13. A spark plug according to claim 12 in which said portion of enlargeddiameter has spiral convolutions adapted to seat on said shoulder.

14. A spark plug according to claim 12 having a metal cap within saidcounterbore with an inturned lip engaging beneath a convolution of saidspring within said counterbore and seating upon said shoulder.

References Cited by the Examiner UNITED STATES PATENTS 1,933,304 10/33Bell 339-252 2,118,673 5/38 Green 313134 X 2,237,362 4/41 Rieman 339-2,336,569 12/43 Rabezzana 313134 X 2,837,679 6/58 Schwartzwalder et al.313-118 X 2,858,361 10/58 v Candelise 313l36 X 2,954,495 9/60 Zeller313136 GEORGE N. WESTBY, Primary Examiner.

1. A SPARK PLUG COMPRISING A CERAMIC INSULATOR HAVING A CENTRAL BOREWITH AN INTERNALLY THREADED PORTION, AN ELECTRODE WITHIN THE BORE OFSAID CERAMIC INSULATOR AND EXTENDING OUTWARDLY FROM ONE END THEREOF, ANELECTRICAL RESISTOR BETWEEN SAID ELECTRODE AND SAID INTERNALLY THREADEDPORTION, AND A COIL SPRING BEARING ON SAID RESISTOR AND HAVINGCONVOLUTIONS DIRECTLY ENGAGING SAID INTERNALLY THREADED PORTION.